Climpact is an R package that calculates indices of daily climate extremes. It can read data for a single site (e.g. a weather station) in the form of a text file, or for gridded data (e.g. from a climate model) in the form of netCDF files. This software directly builds off the R packages climdex.pcic and climdex.pcic.ncdf, developed by the Pacific Climate Impacts Consortium (PCIC).
If you want to calculate these indices from text files then you DO NOT need to install this software, instead go to the Climpact website to calculate these indices online.